The invention is generally directed to toner and developer compositions, and more specifically, the present invention is directed to developer and toner compositions containing charge enhancing additives, which impart or assist in imparting a negative charge to toner particles and enable toners with rapid triboelectric charging characteristics. In embodiments, there are provided in accordance with the present invention toner compositions comprised of toner resins, color pigment particles or dye molecules, and certain aluminum complex composites which serve as negative charge enhancing additives. In embodiments, the present invention is directed to toner compositions with aluminum complex composite charge enhancing additives, which additives can be obtained from the reaction of aluminum ion with a phenol and a hydroxybenzoic acid under basic reaction conditions at a temperature ranging from ambient, about 25.degree. C. to about 100.degree. C. The aluminum complex composite charge enhancing additives in embodiments are believed to be comprised of or contain active aluminum complex components of tetra-coordinated and/or hexa-coordinated aluminum complex anions with mixed ligands derived from hydroxybenzoic acid and phenol, and counter cations of a proton, an alkaline metal ion, or an ammonium ion. The aluminum complex composite charge enhancing additives in embodiments of the present invention enable, for example, toners with rapid triboelectric charging characteristics, extended developer life, stable triboelectrical properties irrespective of changes in environmental conditions, and high image print quality with substantially no background deposits. Also, the aforementioned toner compositions usually contain a colorant component comprised of, for example, carbon black, magnetites, or mixtures thereof, color pigments or dyes of cyan, magenta, yellow, blue, green, red, or brown color, or mixtures thereof thereby providing for the development and generation of black only and colored images. The toner and developer compositions of the present invention can be selected for electrophotographic, especially xerographic, imaging and printing processes, including color processes.
Toners with negative charge additives are known, reference for example U.S. Pat. Nos. 4,411,974 and 4,206,064, the disclosures of which are totally incorporated herein by reference. The '974 patent discloses negatively charged toner compositions comprised of toner resins, color pigments, and as a charge enhancing additive ortho-halophenyl carboxylic acids. Similarly, there are disclosed in the '064 patent toner compositions with chromium, cobalt, and nickel complexes of salicylic acid as negative charge enhancing additives. In U.S. Pat. No. 4,845,003, there are illustrated negatively charged toners with certain aluminum salt charge additives. More specifically, this patent discloses as charge additives aluminum complexes comprised of two or three hydroxybenzoic acid ligands bonded to a central aluminum ion. While these charge additives may have the capability of imparting negative triboelectric charge to toner particles, they are generally not efficient in promoting the rate of triboelectric charging of toner particles. A fast rate of triboelectric charging is particularly crucial for high speed xerographic machines since, for example, these machines consume toner rapidly, and fresh toner has to be constantly added. The added uncharged toners, therefore, must charge up to their equilibrium triboelectric charge level rapidly to ensure no interruption in the xerographic imaging or printing operation. Another disadvantage of these charge additives is their thermal instability, that is they often break down during the thermal extrusion process of the toner manufacturing cycle. Most or many of these and other disadvantages are eliminated, or substantially eliminated with the metal complex charge additives of the present invention.
Developer compositions with charge enhancing additives, which impart a positive charge to the toner particles, are also well known. Thus, for example, there is described in U.S. Pat. No. 3,893,935 the use of quaternary ammonium salts as charge control agents for electrostatic toner compositions; U.S. Pat. No. 4,221,856, which discloses electrophotographic toners containing resin compatible quaternary ammonium compounds in which at least two R radicals are hydrocarbons having from 8 to about 22 carbon atoms, and each other R is a hydrogen or hydrocarbon radical with from 1 to about 8 carbon atoms, and A is an anion, for example, sulfate, sulfonate, nitrate, borate, chlorate, and the halogens such as iodide, chloride and bromide, reference the Abstract of the Disclosure and column 3; a similar teaching is presented in U.S. Pat. No. 4,312,933 which is a division of U.S. Patent 4,291,111; similar teachings are presented in U.S. Pat. No. 4,291,112 wherein A is an anion including, for example, sulfate, sulfonate, nitrate, borate, chlorate, and the halogens; U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference, discloses developer compositions containing as charge enhancing additives organic sulfate and sulfonates, which additives can impart a positive charge to the toner composition; and U.S. Pat. No. 4,298,672, the disclosure of which is totally incorporated herein by reference, discloses positively charged toner compositions with resins and pigment particles, and as charge enhancing additives alkyl pyridinium compounds.
Illustrated in U.S. Pat. No. 5,275,900 is a negatively charged toner composition comprised of a polymer or polymer resins, a colorant or colorants, optional surface additives, and a metal complex charge enhancing additive obtained from the reaction of a hydroxybenzoic acid and a base with a mixture of a metal ion and a hydroxyphenol; U.S. Pat. No. 5,300,387, which discloses a negatively charged toner composition comprised of a polymer or polymers, a colorant or colorants, optional surface additives, and a metal complex charge enhancing additive obtained from the reaction of a hydroxybenzoic acid and a base with a mixture of a metal ion and an aromatic dicarboxylic acid; U.S. Pat. No. 5,238,768, which discloses a negatively charged toner composition comprised of resin particles, colorants, optional surface additives, and a dihydroxyaryl sulfone charge enhancing additive, or an unsymmetrical hydroxyaryl sulfone charge enhancing additive obtained from the condensation of sulfuric acid with a molar equivalent of a phenol, followed by condensation with a second phenol, or from the condensation of an aromatic sulfonic acid with a phenol; U.S. Ser. No. 964,544 (D/92402), which discloses a toner composition comprised of polymers, pigment particles and/or dyes, optional surface additives, and a charge enhancing additive derived from the reaction of a metal, a metal carbonyl, a metal salt, or a metal oxide, with a .beta.-diketone, a .beta.-keto ester, or a malonic ester in an aqueous medium or organic medium; U.S. Pat. No. 5,238,768, which discloses a negatively charged toner composition comprised of a polymer resin or polymer resins, colorants comprised of pigment particles and/or dyes, optional surface additives, and a nonionic zinc complex charge enhancing additive containing two different ligands derived from an ortho-hydroxyphenol and an ortho-hydroxybenzoic acid; U.S. Pat. No. 5,256,575, which discloses a negatively charged toner composition comprised of resin particles, pigment particles, optional surface additives, and a halogenated sailcyclic acid complex charge enhancing additive of the following formula ##STR1## wherein Z is zinc or chromium; M is hydrogen, an alkali metal, an alkaline earth metal, NH.sub.4, or NR.sub.4 wherein R is alkyl; X and Y are independently selected from the group consisting of chloride, iodide and bromide; and n and m are the numbers 1 or 2; U.S. Pat. No. 5,256,514, which discloses a negatively charged toner composition comprised of resin particles, pigment particles, optional surface additives, and a halogenated salicylic acid charge enhancing additive of the following formula ##STR2## wherein X is halogen; M is hydrogen, an alkaline earth, an alkali metal, or NR.sub.4 wherein R is alkyl; and n is the number 1 or 2; and U.S. Pat. No. 5,300,389, which discloses a negatively charged toner composition comprised of resin particles, pigment particles, optional surface additives, and a halogenated aluminum salicylic acid complex charge enhancing additive of the following formulas ##STR3## wherein M is hydrogen, an alkali metal, an alkaline earth metal, NH.sub.4, or NR.sub.4 wherein R is alkyl; X and Y are independently selected from the group consisting of iodide, chloride and bromide, and n and m are the numbers 1 or 2, the disclosures of which are totally incorporated herein by reference.
Known aluminum complexes, such as bis(3,5-di-tert-butylsalicylato)aluminum or bis(4-tert-butylcatecholato)aluminum complexes, may not in many instances be considered acceptable negative charge control agents since, for example, the former has a slow admix time, while the latter generally imparts unacceptably low negative tribo to toners. For example, when used as surface CCA (at 0.1 to 0.25 weight percent level) on a toner comprised of styrene butadiene resin and 6 weight percent of REGAL 330.RTM. carbon black, potassium bis(3,5-di-tert-butylsalicylato)aluminum (III) imparted a negative tribo to the toner of -15 to -40 microcoulombs/gram with polyvinylidene steel coated carrier, however, it could not meaningfully improve the toner's admix time of 2 to 5 minutes. Potassium bis(4-tert-butylcatecholato)aluminum (III) enhanced the toner's admix performance (&gt;15 seconds), but it failed to impart a useful magnitude of negative tribo to the toner (&lt;10 microcoulombs/gram).
While many charge enhancing additives are known, there continues to be a need for charge enhancing additives, which when incorporated in toners provide many of the advantages illustrated herein. There is also a need for negative charge enhancing additives which are useful for incorporation into black and colored toner compositions which can be utilized for developing positive electrostatic latent images. Moreover, there is a need for colored toner compositions containing charge enhancing additives which do not interfere with the color quality of the colorants present in the toners. Another need relates to the provision of toner compositions with certain charge enhancing additives, which toners in embodiments thereof possess substantially stable triboelectric charge levels, and display acceptable rates of triboelectric charging characteristics. Furthermore, there is also a need for toner compositions with charge enhancing additives which possess excellent dispersibility characteristics in toner resins, and can, therefore, form stable dispersions in toner compositions. There is also a need for negatively charged black and colored toner compositions that are useful for incorporation into various imaging processes, inclusive of color xerography, as illustrated in U.S. Pat. No. 4,078,929, the disclosure of which is totally incorporated herein by reference; laser printers; and additionally a need for toner compositions useful in imaging apparatuses having incorporated therein layered photoresponsive imaging members, such as the members illustrated in U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference. Also, there is a need for negative toner compositions which have desirable triboelectric charge levels of, for example, from between about -10 to about -40 microcoulombs per gram, and triboelectric charging rates of less about 120 seconds, and preferably less than 60 seconds as measured by standard charge spectrograph methods when the toners are frictionally charged against suitable carrier particles via roll milling. There is also a need for nontoxic, substantially nontoxic, or environmentally compatible charge enhancing additives which when incorporated at effective concentrations of, for example, less than 10 weight percent, and preferably less than 5 weight percent in toners, such as 0.1 to about 3 weight percent, render the toners to be environmentally acceptable. An additional need resides in the provision of simple and cost-effective preparative processes for the aluminum complex composite charge enhancing additives of the present invention. The concentrations of the charge enhancing additives that may be incorporated into the toner compositions generally range from about 0.05 weight percent to about 5 weight percent, depending on whether the charge additive is utilized as a surface additive or as a dispersion in the bulk of the toner. The effective concentrations of toner in the developer, that is toner and carrier particles, are, for example, from about 0.5 to about 5 weight percent, and preferably from about 1 to about 3 weight percent.